Magnetoelastic Torquemeter System for LCAC Hovercraft Turboshaft Engine Monitoring and Control

Abstract

This paper presents the development of a magnetoelastic torque-meter for use on the Landing Craft Air Cushion (LCAC) hovercraft’s high speed gas turbine engines. As the gas turbine can produce in excess of the nominal torque limit of the right angle gearbox, torque limiting is required. Limiting torque based on torque tables (as is done currently) penalizes the overall performance of the majority of the fleet due to a significant variance in engine output horsepower. This sub-optimal operation of the craft could be overcome by measuring actual torque produced by each engine with a torque-meter; however conventional torque-meter designs were deemed impractical to retrofit due to the design requirements, and issues with integration and reliability / maintainability. An in-depth search by the US Navy identified a torque-meter concept utilizing magnetoelastic polarized band technology. The aim of this paper is to: (i) outline the general architecture of the system, (ii) highlight the performance of the torque-meter developed for the LCAC, (iii) describe the efforts that helped to mature this technology to Technology Readiness Level 8 and to transition it from motorsport applications to use on the LCAC, and (iv) summarize the initial results of the torque-meter system validation obtained through dynamometer tests on the engine and craft tests on the LCAC.